Casting roller with active profile control

ABSTRACT

The invention relates to a casting roll ( 1 ) for the casting of metal strip in the casting gap between two casting rolls with variable separation which are parallel and which can be cooled. The casting roll comprises a roll axle ( 3 ) with a roll casing ( 2 ) surrounding said axle and with adjustable convexity of the peripheral surface of said roll casing during operation by means of a hydraulic pressure cushion ( 14 ). The rotatable roll axle ( 3 ) is designed with a cylinder ( 9 ), comprising a piston ( 10 ), on at least one side ( 5, 7 ) of the casting roll ( 1 ), and a power system ( 11 ) is provided for exertion via the pistons ( 10 ) on the pressure medium to influence the convexity of the roll casing ( 2 ).

The invention relates to a casting roller of a casting machine for casting metal strip, comprising a roller axis with a roller casing surrounding the roller axis, with a circumferential surface whose crown is adjustable during casting operations by means of a hydraulic pressure cushion, and to a method for operating the casting roller.

In the context of the description of the invention, the crown of the casting roller will in the following also be referred to as profile.

The casting thicknesses of 1 to 4 mm do not permit a change of the oversize of the profile in the subsequent rolling operation. For this reason, the desired profile oversize of 1 to 2% of the rolled thickness must already be present in the cast strip. Therefore, in the known casting rollers with rotating roller axis, the positive roller camber occurring during casting, is compensated by a negative roller grinding in order to adjust the desired profile oversize of the cast thickness. The negative roller grinding is carried out for a computed temperature profile of the casting roller, based on operation results. If deviating and/or changing heat flux densities occur during the casting operation, the resulting temperature profile of the casting roller results in a profile oversize of the casting thickness which is outside of the desired range of 1 to 2 percent. In plants which are in operation the profile oversize is frequently outside of the required range.

STATE OF THE ART

A casting roller for casting metal strip in the casting gap between two parallel casting rollers which can be cooled and whose distance can be adjusted, further comprising a shaft with a sleeve surrounding one of these casting rollers at a radial distance and an outer casing with a camber of its circumferential surface which is adjustable during the casting operation by means of hydraulic pressure elements, as well as means for connecting the pressure element to an external hydraulic pressure generating system, is known from EP 1 347 851 B1. In this casting roller, axially spaced apart radial combs are provided between sleeve and casing. Moreover, belts are arranged between the sleeve and the radial combs, wherein the belts are deformable by a hydraulic medium, such that the belts exert radial forces when a pressure is applied to them, wherein, in turn, the pressure application results in a change of the camber of the casing of the casting roller.

It is known from WO 02/43 902 A1 to conduct a pressure medium over an annular rotation passage included rotating metal roller casing. The pressure medium is conducted from there through bores into the profiled hollow space of the outer roller casing and the roller profile is changed in dependence on the pressure of the medium. A pressure of up to 1000 bar is required for changing the roller profile. This solution has the disadvantage that a leakage-free operation of the rotation passages is virtually impossible during longer periods of operation.

In DE 38 39 119 A1, the pressure medium is conducted through a rotation passage for changing the roller profile, as is the case in WO 02/43902 A1.

Also in JP 59 113 963 A, the pressure medium for changing the roller profile, the pressure medium is conducted through a rotation passage, as is the case in WO 02/43 902 A1. The pressure of the medium is changed in dependence on the bearing forces which are measured by means of load cells underneath the bearing housings.

WO 03/024 645 A1 describes a roller with vertical axis on which the roller casing is rotatably arranged, as described in WO 03/024 654. Several roller pairings with surrounding spacer rings are arranged between the axis and the roller casing. The pressure medium is conducted through the vertical axis into the pressure cushion between the axis and the pressure ring. The enlargement of the pressure ring is transmitted through the roller bearing and the spacer ring to the roller casing. The expansion of the roller casing takes place in this solution through a roller bearing which is under relatively high load (friction losses, heating and wear off the bearings).

OBJECT

The invention is based on the task of providing a casting roller with rotating roller axis in which an active control/change of the roller profile is possible during the casting operation. The purpose of this is to maintain a predetermined profile oversize of 1 to 2% even in the case of deviating and/or changing heat flux densities or temperature profiles in the roller casing. Because of the required high pressures, the profile control by means of a pressure medium should not take place through a rotating connection in order to avoid leakage or losses. The efficiency of the casting roller plant is to be improved.

In accordance with the invention, this task is solved in that in a casting roller of a casting machine for casting metal strip, comprising a roller axis with a roller casing surrounding the roller axis, with a camber of its circumferential surface which is adjustable during the casting operation by means of hydraulic pressure cushions on the drive-fee side of the casting roller, wherein the rotating roller axis has a cylinder with a piston, wherein a power system is provided for influencing a pressure medium through the piston for influencing the camber of the roller casing.

In contrast to the prior art, the present invention proposes arranging a piston in a rotating roller axis with a roller casing of a casting roller preferably on the drive-free side, wherein the piston is moved axially for generating pressure. This is a high-pressure system in which the pressure is produced in a closed system in the rotating roller axis.

The invention makes it possible to produce in an operationally safe manner a pressure of 1000 bar and more without leakage or losses.

The displacement of the piston in the rotating axis preferably takes place through a hydraulic cylinder arranged laterally next to the axis. Since the piston rotates with the axis, a pressure bearing (axial bearing) must be arranged between the rotating piston of the roller axis and the piston of the hydraulic cylinder. The diameter of the piston of the hydraulic cylinder is essentially freely selectable. Consequently, with a larger diameter of the piston of the hydraulic cylinder as compared to the diameter of the piston of the roller axis, it is possible to produce with a lower pressure in the hydraulic cylinder a significantly higher pressure in the cylinder on the roller axis (pressure increase in comparison to the cylinder surface/piston surface).

Further embodiments of the device result from the respective dependent claims.

Further details, features and advantages of the invention result form the following explanations of an embodiment which is schematically illustrated in the drawings:

In the drawing:

FIG. 1 shows a side view of a casting roller according to the invention with a right driven side and a left drive-free side;

FIG. 2 shows a detail of the roller casing with and without pressure application; and

FIG. 3 is a sectional view of the side of the casting roller on the left driven side.

FIG. 1 shows a casting roller 1 of a casting machine with two casting rollers. The casting roller 1 is composed of a roller casing 2 and a roller axis 3 which is received in two bearing housings 4. Arranged on the right driven side 5 is a flange 6 for universal joint shafts (not shown) for rotating the casting roller 1. Arranged on the left drive-free side 7 is a water supply/water discharge 8 for cooling the casting roller 1. On the left end of the drive-free side 7 of the roller axis 3 is a cylinder 9 for producing the pressure for influencing the profile of the roller casing 2. A power system 11 for generating a defined pressure act on a piston on the roller axis 10 in the cylinder 9.

FIG. 2 shows the profile of the roller casing 2. A first contour 12 shows the negative casting roller grinding without pressure application of the roller casing 2. A second contour 13 shows the casting roller profile with a pressure application of the roller casing 2. This makes it possible to adjust the casting roller profile for adjusting the desired profile of a cast strip in a targeted manner.

FIG. 3 shows that the roller casing 2 is arranged on the roller axis 3. One or more pressure cushions 14 are provided between the roller axis 3 and the roller casing 2. The pressure cushions 14 are preferably symmetrically annular relative to the vertical axis in the shape of a ring. The width 22 of the pressure cushion 14 or of several pressure cushions 14 is narrower than the width 23 of the roller casing 2 as seen in FIG. 1, in order to provide space for sealing devices and the like between the roller casing 2 and roller axis 3. The term width is used as indicating the length in axial direction. The pressure cushion or the pressure cushions 14 are connected to a pressure chamber 16 through bores 15. A pressure medium is provided in the pressure chamber 16, the bores 16 and the pressure cushions 14 which form a closed system. For filling the system with a pressure medium and for ventilating, bores 17 are provided in the roller casing 2 which are closed by means of a plug 18 after filling and ventilating. In order to prevent the pressure medium from flowing back into the cylinder 9, a check valve can be arranged in the piston 10.

The roller axis 3 is rotatably mounted in a roller bearing 19 which is arranged in the bearing housing 4. The cylinder 9 is flanged to the free end of the roller axis 3. The piston 10 of the axis 3 is axially slidably mounted in the cylinder 9; the piston 10 delimits the pressure chamber 16 in the cylinder 9. Cylinder 9 can be a plunger or a differential cylinder. Through the power system 11 which is mounted stationary next to the casting roller 1 or directly at the casting roller 1, a defined pressure is produced to act on the piston 10 on the roller axis 3 and through the latter in the pressure chamber 16. The power system 11 is a hydraulic cylinder 14 whose piston 25 acts on the piston 10 of the roller axis 3. Since the piston 10 rotates together with the roller axis 3, a pressure bearing 16 (axial bearing) is mounted between the piston 25 of the hydraulic cylinder 24 and the piston 10 of the roller axis 3. The pressure medium is also conducted into the annular pressure cushions 13 through the bores 15, wherein the pressure cushions influence in a targeted manner the contour 12, 13 of the roller casing 2 in dependence on the pressure.

A pipe for water supply of the cooling of the casting roller 1 is inserted into a core removing hole 21. The supply and discharge of the cooling water takes place through the water supply/water discharge 8 on a peg 20 of the roller axis 3.

The law of actio=reactio applies between the two pistons 10 and 24; in other words, the force F₂₅, by means of which the piston 25 of the hydraulic cylinder 24 acts on the piston 10 of the roller axis 3 is the same as the force F₁₀ by means of which the piston 10 presses on the piston 25. Mathematically expressed, the following applies:

|F ₂₅ |=|F ₁₀|  (1)

Expressed physically, a force is the product of pressure×surface, so that equation (1) can be reformulated as follows:

$\begin{matrix} {{P_{{Hydraulic}\mspace{14mu} {Cylinder}\mspace{14mu} 24} \cdot {II} \cdot \left( \frac{\varphi \mspace{20mu} {Piston}\mspace{20mu} 25}{2} \right)^{2}} = {P_{{Hydraulic}\mspace{14mu} {Cylinder}\mspace{14mu} 9} \cdot {II} \cdot \left( \frac{\varphi \mspace{20mu} {Piston}\mspace{20mu} 10}{2} \right)^{2}}} & (2) \\ {\mspace{79mu} {P_{{Cylinder}\mspace{14mu} 9} = {\frac{P_{{Hydraulic}\mspace{14mu} {Cylinder}\mspace{11mu} 24}}{1} \cdot \left( \frac{\varphi \mspace{20mu} {Piston}\mspace{20mu} 25}{\varphi \mspace{20mu} {Piston}\mspace{20mu} 10} \right)^{2}}}} & (3) \end{matrix}$

wherein,

P_(cylinder 9) refers to the pressure in the cylinder 9 on the roller axis 3;

P_(hydraulic cylinder 24) refers to the pressure in the hydraulic cylinder 24;

Ø_(piston 25) refers to the diameter of the piston 25 of the hydraulic cylinder 24;

Ø_(piston 10) refers to the diameter of the piston 10 of the cylinder 9 on the roller axis 3.

The diameter of the piston 25 of the hydraulic cylinder 24 is essentially freely selectable. Consequently, it is possible to produce with a greater diameter of the piston 25 of the hydraulic cylinder 24 in comparison to the diameter of the piston 10 of the roller axis 3 a significantly higher pressure in the cylinder 9 on the roller axis 3 or in the pressure chamber 16 by using a lower pressure in the hydraulic cylinder 24 (pressure increase in relation to the piston surface of hydraulic cylinder/piston surface of cylinder at the roller axis).

In accordance with formula 3, the pressure P_(cylinder 9) acting on the piston 10 of the cylinder 9 depends on the pressure P_(hydraulic cylinder 24) in the outer hydraulic cylinder 24 and the ratio of the diameter of the piston 25 of the hydraulic on the roller axis 3.

The change of the radius OR of the roller casing 2 is a function of the pressure in the cylinder 9 of the roller axis 3 and, thus, in the pressure chamber 16, so that the following applies:

$\begin{matrix} \begin{matrix} {{\Delta \; R} = {f\left( P_{{Cylinder}\mspace{14mu} 9} \right)}} \\ {= {f\left( {P_{{Cylinder}\mspace{14mu} 9} = {\frac{P_{{Hydraulic}\mspace{14mu} {Cylinder}\mspace{11mu} 24}}{1} \cdot \left( \frac{\varphi \mspace{20mu} {Piston}\mspace{20mu} 25}{\varphi \mspace{20mu} {Piston}\mspace{20mu} 10} \right)^{2}}} \right)}} \end{matrix} & \begin{matrix} (4) \\ (5) \end{matrix} \end{matrix}$

An adjustment through a combination of motor, gearing, and spindle makes possible a defined distance adjustment; however, the pressure adjustment in the roller axis 3 resulting from the defining distance remains undefined.

LIST OF REFERENCE NUMERALS

-   1 casting roller -   2 roller case -   3 roller axis -   4 bearing housing -   5 driven side -   6 flange -   7 driven-free side -   8 water supply/water discharge -   9 cylinder -   10 piston -   11 power system -   12 first contour -   13 second contour -   14 pressure cushion -   15 bores -   16 pressure chamber -   17 bores -   18 plug -   19 roller bearing -   20 peg -   21 removing hole -   22 width of pressure cushion -   23 width of roller casing -   24 hydraulic cylinder -   25 piston -   26 pressure bearing 

1. Casting roller (1) of a casting machine for casting metal strip, comprising a roller axis (3) with a roller casing (2) surrounding the roller axis (3), with a camber of its circumferential surface adjustable during the casting operation with hydraulic pressure cushions (14), wherein on at least one side (5, 7) of the casting roller (1) the rotating roller axis (3) is formed with a cylinder (9) which has a piston (10), and a power system (11) is provided for influencing the crown of the roller casing (2) by acting through the piston (10) on a pressure medium.
 2. Casting roller according to claim 1, wherein the power system (11) is a hydraulic cylinder.
 3. Casting roller according to claim 1, wherein at least one annular pressure cushion (14) is arranged over the width of the roller axis (2).
 4. Casting roller according to claim 1, wherein the width of the pressure cushion 14 is at least 80 mm smaller than the width of the roller casing (2).
 5. Casting roller according to claim 1, wherein several annular pressure cushions (14) with preferably different widths are arranged over the width of the roller axis (3).
 6. Casting roller according to claim 1, wherein the annular pressure cushions (14) have an increasing width toward the middle of the roller axis.
 7. Casting roller according to claim 1, wherein the ratio of the maximum and minimum width of the pressure cushions (14) is smaller than
 4. 8. Casting roller according to claim 1, wherein the annular pressure cushion (14) or the annular pressure cushions (14) are arranged between the roller axis (3) and the roller casing (2).
 9. Casting roller according to claim 1, wherein the radial distance in the area of the annular pressure pistons (14) between the roller axis (3) and the roller casing (2) is greater than 0.5 mm and smaller than 5 mm.
 10. Casting roller according to claim 1, wherein the piston (10) has a diameter of between 20 and 100 mm.
 11. Casting roller according to claim 1, wherein a check valve is arranged in the piston (10).
 12. Casting roller according to claim 1, wherein the cylinder (9) and the power system (11) are arranged on the drive-free side (7).
 13. Method of operating a casting roller according to claim 1, wherein for ventilating the pressure system the pressure medium is supplied through the piston (10) and is discharged through each pressure cushion (14) through the roller casing (2).
 14. Method according to claim 1, wherein pressure is applied to the pressure system after the assembly of the casting roller (1).
 15. Casting roller according to claim 13, wherein the pressure system is constructed for a maximum pressure of 1000 bar.
 16. Method according to claim 13, wherein the pressure is adjusted in dependence on the diameter of the piston (10) in proportion to the force of the power system (11). 